1. Field of the Invention
The present invention relates to an air conditioner performing heating or cooling by using a heat pump cycle, and more particularly, to an air conditioner provided with an outdoor unit and performing its own defrosting operation at the time of heating.
2. Description of the Conventional Art
Generally, an air conditioner is a device for controlling temperature, humidity, current, and cleanliness of air for comfortable indoor circumstances. By a construction of a unit, the air conditioner is divided into an integral type air conditioner for accommodating both an indoor unit and an outdoor unit in a single case, and a separated type air conditioner for constituting a compressor and a condenser as an outdoor unit and constituting an evaporator as an indoor unit. Addition to this, there is an air conditioner for both heating and cooling which can selectively perform heating and cooling by switching a refrigerant path with a four-way valve.
Recently, a multi-type air conditioner provided with a plurality of indoor units for heating or cooling according to each indoor space is being used. The multi-type air conditioner is provided with a plurality of compressors or a plurality of outdoor units connected to each other in parallel in order to effectively perform heating or cooling correspondingly to the number of the indoor units.
FIG. 1 is a schematic view showing one embodiment of an air conditioner in accordance with the conventional art. As shown, the conventional air conditioner is divided into an indoor unit 11 and an outdoor unit 21, and the indoor unit 11 is composed of an indoor heat exchanger 13 for heat-exchanging a refrigerant indoors and an indoor expansion device 15 for depressurization-expanding a refrigerant.
The outdoor unit 21 is composed of a compressor 23 for compressing refrigerant gas, an outdoor heat exchanger 33 for heat-exchanging a refrigerant with external air, a four-way valve 31 adjacently arranged to the compressor 23 for circulating a compression refrigerant discharged from the compressor 23 according to a heating cycle or a cooling cycle, an accumulator 35 arranged at an inlet of the compressor 23 for filtering a liquefied refrigerant, a first refrigerant path 41 for connecting the outdoor heat exchanger 33 to the indoor unit 11, and a second refrigerant path 42 for connecting the four-way valve 31 to the indoor unit 11.
Also, an oil separator 22 for separating oil, an oil returning path 29 for recycling oil separated by the oil separator 22 into the compressor 23, and a check valve 27 for preventing a backflow of a refrigerant are installed between an outlet of the compressor 23 and the four-way valve 31.
A receiver 37 for temporarily receiving a refrigerant and a drier 39 for removing moisture included in a refrigerant are installed in the middle of the first refrigerant path 41, and service valves 45a and 45b are respectively installed at the first and second refrigerant paths 41 and 42.
Both heating and cooling are operated in said conventional air conditioner. First, in case of the cooling operation, a refrigerant compressed in the compressor 23 is introduced into the outdoor heat exchanger 33 by an operation of the four-way valve 31, and the refrigerant which has passed through the outdoor heat exchanger 33 is introduced into the indoor expansion device 15 and the indoor heat exchanger 13 of the indoor unit 11 through the first refrigerant path 41. Also, the refrigerant which has passed through the indoor unit 11 is introduced into the four-way valve 31 through the second refrigerant flow 42, and the refrigerant which has passed through the four-way valve 31 passes through the accumulator 35 thus to be introduced into the compressor 23. Accordingly, by said cooling cycle of a refrigerant, the cooling operation of the air conditioner is performed.
Also, in case of the heating operation, a refrigerant compressed in the compressor 23 passes through the indoor expansion device 15 and the indoor heat exchanger 13 of the indoor unit 11 through the second refrigerant path 42 by the four-way valve 31, and a refrigerant discharged from the indoor unit 11 is introduced into the outdoor heat exchanger 33 through the firs refrigerant path 41. The refrigerant which has passed through the outdoor heat exchanger 33 passes through the four-way valve 31 and the accumulator 35 thus to be introduced into the compressor 23. Accordingly, by said heating cycle of a refrigerant, the heating operation of the air conditioner is performed.
Meanwhile, during the heating operation, frost is generated on a surface of the outdoor heat exchanger 33, and in order to remove the frost, the heating operation is periodically stopped and a defrosting operation is performed. A defrosting cycle of a refrigerant for performing the defrosting operation is formed of a reverse cycle of the heating cycle like the cooling cycle.
FIG. 2 is a schematic view showing another embodiment of the air conditioner in accordance with the conventional art. As shown, a plurality of outdoor units 21 having the same structure as the aforementioned embodiment are installed in parallel in order to enhance efficiency of the air conditioner in case that a great cooling/heating capacity is required. Also, each outdoor unit 21 is connected to main paths 48 and 47 for introducing and discharging a refrigerant into the indoor unit 11 thus to perform cooling and heating operations.
In said conventional air conditioner, a refrigerant which has performed the defrosting operation of the outdoor heat exchanger 33 passes through the indoor expansion device 15 and the indoor heat exchanger 13 of the indoor unit 11. Accordingly, when the defrosting operation is performed after stopping the heating operation, a refrigerant which circulates through the indoor expansion device 15 and the indoor heat exchanger 13 during the heating operation is at once reversely circulated thus to cause noise of the indoor unit 11.
Moreover, in case that a plurality of the outdoor units 21 of the air conditioner are arranged, when one outdoor unit 21 among the plurality of outdoor units 21 performs the defrosting operation, the heating operation of all the outdoor units 21 has to be stopped and the defrosting operation has to be simultaneously performed. Accordingly, the heating operation of the plurality of indoor units 11 connected to the outdoor units 21 is all stopped thus to generate indoor heat loss.